The aforesaid crank drive system of a shaft of a microtome is used in particular in the context of a sliding microtome of the Applicant, namely in the “Leica SM2000R” model. This sliding microtome is described in printed form in a company brochure of March 2003. In a sliding microtome, the knife that sections the specimen is moved back and forth on a movably arranged slide in order to section the specimen arranged in a specimen holder. The specimen holder is moved vertically onto the knife via a corresponding mechanism, namely a micrometer mechanism; this is also referred to as “advance.” The increment with which the specimen is advanced toward the knife can be set to an accuracy of 0.5 μm via a rotary knob fitted with a scale. Provided on the aforementioned sliding microtome as a further operating element is a crank with which a coarse drive mode for specimen movement toward the knife or away from the knife, i.e. substantially in a vertical direction, can be realized. It is possible as a result, after a sample change, to advance the specimen holder along with the specimen rapidly onto the knife, so that sectioning operations with a definable desired cut thickness can directly follow one another. Provided as a further operating element is a lever (activation lever), guided in an elongated hole and having a knob, with which a manual advance motion of the specimen holder toward the knife can be activated. This knob or lever is usually utilized only in the context of advance in sectioning mode, the advance occurring at the increment currently set using the rotary knob fitted with the scale. This sliding microtome also encompasses an operating state with automatic advance, the operating element relevant thereto being arranged on the microtome slide. This automatic advance is usually utilized upon initial cutting of the sample, and replaces actuation of the activation lever.
With regard to the crank drive system for coarse drive, it is at present possible to produce an advance only upon a clockwise rotation. Correspondingly, upon a counterclockwise rotation of the crank drive system, the specimen or specimen holder is moved away from the knife or lowered. It may, however, be desirable to allow an advance of the specimen also to be produced with a counterclockwise rotation, for example because different operators operate a single sliding microtome, and one operator is left-handed and another operator right-handed. Such a requirement at present can be met only by making available two different sliding microtomes, specifically such that with the one sliding microtome an advance is produced by rotating the crank clockwise, and in the case of the other sliding microtome a counterclockwise rotation of the crank produces a respective advance. The rotation direction of the crank drive system is therefore permanently defined in terms of the design.